The present invention relates to an instruction beam detection apparatus and a method of detecting an instruction beam. More specifically, the present invention relates to an instruction beam detection apparatus capable of detecting an instruction beam irradiated from a remote control device having a light source for irradiating the instruction beam in a non-visible light wave length range and an operation portion for controlling the light source to irradiate the instruction beam. Further, the present invention relates to a method of detecting an instruction beam applicable to the instruction beam detection apparatus.
In general, a remote control device (a remote controlling device) is provided with a light source for irradiating an infrared light beam, so that the remote control device is capable of remotely controlling an electric device such as a television set, an audio visual device and the like. Further, such a remote control device is provided with a plurality of operation buttons for inputting an instruction (a command) to the electric device.
When an operator operates specific one of the operation buttons, the light source irradiates the infrared light beam having a signal wave shape corresponding to the specific one of the operation buttons. When the electric device receives the infrared light beam, an infrared light sensor regenerates the signal wave shape of the infrared light beam thus received from the remote control device. Accordingly, the electric device recognizes the command transmitted from the remote control device, and performs a process according to the command.
In the remote control device having the configuration described above, when the number of the commands is increased due to an increase in functions of the electric device, it is necessary to increase the number of the operation buttons. As a result, when the remote control device is operated to transmit the commands to the electric device, it is difficult for the operator to recognize the operation buttons necessary for transmitting the commands.
To this end, a conventional technology has been proposed, in which the remote control device is configured to function as a pointing device. For example, Patent Reference 1 has disclosed such a conventional technology. According to Patent Reference 1, instead of the infrared light sensor, an imaging element is provided for capturing an image of an indicator member disposed in a moving object, and a display unit is provided for displaying an image output as well as the indicator member as a cursor.
Patent Reference 2 has disclosed an image display control device. The image display control device controls an image display device to display an operation menu on a liquid crystal display portion thereof. Further, a camera with an infrared light filter is provided for recognizing an infrared light signal transmitted from the remote control device. Further, the image display control device is configured to identify a position of the remote control device in a captured image according to the recognition result of the infrared light signal, so that the position of the remote control device is displayed on the liquid crystal display portion. Accordingly, it is possible to determine an operation specified position of the operation menu.
Patent Reference 3 has disclosed a game operation device. The game operation device is provided with an image capture unit capable of capturing an image in a direction along a longitudinal direction of a housing of the remote control device, so that the image capture unit captures an infrared light beam transmitted from an LED module to obtain an image signal. Accordingly, it is possible to capture an operation signal varying depending on a position or a posture of the remote control device through processing the image signal.
Patent Reference 1: Japanese Patent Publication No. 04-123121
Patent Reference 2: Japanese Patent Publication No. 2007-013652
Patent Reference 3: Japanese Patent Publication No. 2007-054114
FIG. 11 is a graph showing a relationship between an irradiation spectrum intensity (a relative value) and a wave length (an irradiation spectrum intensity characteristic) of sun light, the fluorescent light (white), and LED light, and a relationship between a spectral sensitivity (an absolute value) and the wave length (a spectral sensitivity characteristic) of crystal silicon and a human eye.
As shown in FIG. 11, the infrared light sensor formed of crystal silicon has the spectral sensitivity at a relatively high level relative to near infrared light having a wave length of 940 nm. Further, as presented as the sun light and the fluorescent light (white) in FIG. 11, environmental light such as the sun light and the fluorescent light (white) contains near infrared light having the intensity at a relatively low level. Accordingly, conventionally, the remote control device is provided with the light source formed of an LED for irradiating the LED light as an instruction beam shown in FIG. 11.
As shown in FIG. 11, the LED light contains near infrared light having the intensity at a relatively high level (refer to the LED spectrum in FIG. 11). Accordingly, it is possible to secure a sufficient S/N (noise to signal) ratio relative to the environmental light as a noise component.
Accordingly, in the conventional technology disclosed in Patent References 1 and 2, when the imaging element formed of a CCD or a CMOS is provided for detecting the position of the instruction beam irradiated from the remote control device, it is preferred to use the near infrared light as the instruction beam. In this case, however, when the imaging element detects the position of the instruction beam, the instruction beam is irradiated on only a part of pixels (optical electric conversion cells) among a large number of the pixels disposed on a light receiving surface of the imaging element. Further, the instruction beam does not tend to be stably irradiated on specific ones of the pixels on the light receiving surface. Still further, in many cases, the electric device, that is the target of the remote control of the remote control device, is placed in an environment where environmental light such as the sun light, room illumination, and the like is irradiated on the light receiving surface of the imaging element.
In the conventional technology, when the imaging element captures infrared light, a short wave length cutting filter may be disposed in an optical system for reducing a visible light component. However, as explained above, when the instruction beam is irradiated only on a part of the light receiving surface of the imaging element, or is not stably irradiated on the specific location of the imaging element, even though the short wave length cutting filter is disposed, it is difficult to selectively detect the instruction beam to determine the position or the change thereof. Further, in order to improve the S/N ratio relative to the environmental light, the luminous intensity of the instruction beam may be increased. However, in this case, the life of an internal battery of the remote control device tends to be shortened.
In view of the problems described above, an object of the present invention is to provide an instruction beam detection apparatus and a method of detecting an instruction beam capable of solving the problems of the conventional instruction beam detection apparatus. In the present invention, when an imaging element of the instruction beam detection apparatus detects a position of the instruction beam, it is possible to detect the position of the instruction beam with a higher degree of accuracy while reducing an influence of the environmental light.
Further objects and advantages of the present invention will be apparent from the following description of the present invention.